Secondary packing for a mechanical seal

ABSTRACT

Secondary packing for a mechanical seal. There are provided at least two annular packing components within the normal secondary packing receptacle in a mechanical seal, one of which sealingly engages the seal ring but only lightly touches, or is free from contact with, the shaft, the other sealingly engages the shaft but only lightly touches, or is free from engagement with, the seal ring, and the two components are in sealing engagement with each other. Preferably, the component engaging the seal ring is of a hard and stiff material, such as graphite, while the component engaging the shaft is of a softer nature, such as a fluorocarbon or rubber.

United States Patent [191 Hershey SECONDARY PACKING FOR A MECHANICALSEAL I [52] US. Cl. 277/87 [51] Int. Cl. Fl6j 15/34, Fl6j 1 5/38 [58]Field of Search 277/81, 86, 87, 85, 93,

[56] References Cited UNITED STATES PATENTS 12/1962 Woodcock etal 277/936/1959 Jensen ..277/40 Apr. 30, 1974 Primary ExaminerLouis R. PrinceAssistant Examiner-Robert l. Smith Attorney, Agent, or Firm-Woodhams,Blanchard & Flynn 57] ABSTRACT Secondary packing for a mechanical seal.There are provided at least two annular packing components within thenormal secondary packing receptacle in a mechanical seal, one of whichsealingly engages the seal ring but only lightly touches, or is freefrom contact with, the shaft, the other sealingly engages the shaft butonly lightly touches, or is free from engagement with, the seal ring,and the two components are in sealing engagement with each other.Preferably, the component engaging the seal ring is of a hard and stiffmaterial, such as graphite, while the component engaging the shaft is ofa softer nature, such as a fluorocarbon or rubber.

13 Claims, 3 Drawing Figures SECONDARY PACKING FORv A MECHANICAL SEALFIELD OF THE INVENTION Thisinvention relates to a secondary shaftpacking for a mechanical seal'and particularly to a type thereof havingat least two cooperating components, one thereof bearing snugly andtightly against the rotating sealing member of the mechanical seal,another bearing snugly and tightly against the shaft and said twocomponents bearing against each other in a flexible sealingrelationship.

BACKGROUND OF THE INVENTION Mechanical seals have been known to the artfor over sixty years and have been of widespread application for thestuffing boxes of pumps, autoclaves, mixers or similar uses for overthirty years. While such seals have assumed a wide variety of forms, onecommon type which has widespread industrial use for all of such periodutilizes one sealing ring which is fixed and sealed with respect to themachine being sealed and a second sealing ring operating in cooperationwith said first-mentioned sealing ring, which second sealing ringencircles the shaft and rotates therewith. Means are provided for urgingsaid second, or rotating, sealing ring against the fixed sealing ringand further means are provided, normally termed secondary packing orshaft packing, positioned between said rotating sealing member and theshaft for sealing against the passage .of fluid therebetween.

This secondary packing is normally chosen according to the materialbeing handled by the pump, or other machine in question, and accordingto the conditions of temperature and pressure under which the seal isexpected to operate. All of this is well known to the art and theselection of such secondary packing has been a subject of extensivestudy from the beginning.

In many cases such secondary packing comprises 0- rings which may be ofnatural rubber, synthetic rubber or various other materials known to theart. In such case, while seals have operated under many conditions witha high degree of success utilizing this type of secondary packing,there-is often a tendency where high pressures or high temperature areencountered for the O-ring material to yield to the normal operatingpressure of the system and extrude between the seal ring and the shaftand/or between the shaft and the means, often termed a compression ring,by which sealing pres sure is placed onto said secondary packing andtransferred therethrough to urge the rotating sealing ring 4 against thefixed sealing ring. This problem of extrusion is well recognized and haslong beenknown often to provide def nite limitations onto thetemperature or pressure which a given seal is capable of handling.

Many attempts have been made in the past to provide a secondary packinghaving a greater capacity for withstanding temperature and/or pressureand such packings have included ring or spiral packings of variousshapes, such as of square or chevron cross-section, or othercross-sections attempting to utilize the pressure of liquid beinghandled to improve the sealing effect thereof.

To the same-ends, such packings have also been made of a wide range ofother materials. A recent and highly effective packing for this purposecomprises a The seal utilizing this last-mentioned shaft packing,however, effective though it is for many purposes, still has certaindisadvantages which were common also to previously known seals andwhich, as with previously known seals often limits the conditions underwhich mechanical seals so equipped may be effectively used. Among thesedisadvantages, one of the principle ones is the so-called hangup'by thesecondary packing as the seal otherwise attempts to move along the shaftto compensate for wear between the respectively rotating sealing faces.Under the normal pressure applied to the shaft packing, same is urgedtightly against the shaft in order to create an effective seal and overthe course of time this packing often tends to seize or grip onto theshaft tightly and it becomes impossible, even at a pressure within thestuffing box of only 50 p.s.i. for the packing to move axially along theshaft as necessary to compensate for wear. This problem is particularlyprevalent in balanced seals and occurs occasionally in unbalanced seals.Further, in instances where material leaks through the seal and hardenson the shaft, the graphite material may respond to the normal wobble ofthe seal ring and wear or degrade against the hardened deposits. Thiscan eventually destroy the seal between the packing and the shaft andpermit serious leakage. Thus, the seal is in many cases effective onlyfor a period of time less than that for which it is inherently capableof operating and provides a point at which improvement is desired. I

Afurther problem lies in the fact that where a secondary packing hassome degree of rigidity, as contrasted to the relatively soft andthereby extrudable rubber O- rings,'it will tend to move slightly withrespect either to the shaft or to the rotating sealing member, or both,in response to normal relative movement between the rotating sealingring and the shaft and thereby result in fretting of either or both ofthe shaft or the surface of the rotating sealing ring against which thesecondary packing is urged. This occurs even with stainless steel ringsor shafts and provides potential areas of leakage. Further, thisfretting is often-erratic in that it depends in many instances upon themanner in which a seal is installed and hence one seal may operateeffectively and without leakage for a relatively long period of timewhereas another identical seal under identical conditions may fail as aresult of fretting within a matter of a few hours.

In an attempt to meetthe foregoing problems and others arising out ofthe secondary packing which are well known to the industry, certain ofthose skilled in the art have attempted to eliminate secondary packingentirely and to provide 'a flexible metallic bellows between therotating sealing ring and a suitable annular member which is fixed withrespect to the shaft. Such bellows structure permits the desiredmovement of the rotating sealing ring with respect to the shaft and yeteliminates the need for shaft packing of the kind abovedescribed. Thistype of seal has been especially popular in connection with highpressures, high temperatures or highly corrosive fluids, such as but notconfined to those often used in connection with nuclear equipment.However, these seals also have inherent difiiculties, primarily in thatthe necessary flexing of the metal comprising the bellows willeventually generate minor breaking points or pinholes therethroughresulting in leakage and breakdown of the seal.

Accordingly, it has long been desirable to provide a seal capable ofmeeting the following objectives:

1. To provide a secondary packing for a mechanical seal which is capableof long and reliable operation under adverse conditions including one ormore of high temperature, high pressure and corrosive fluid in contactwith the seal parts.

2. To provide a secondary packing for a mechanical seal which willoperate at a temperature and/or pressure, or in contact with a corrosivefluid, to at least the same extent and/or degree as that capable ofbeing met by the remainder of the seal parts.

3. To provide a secondary packing for a mechanical seal which willprovide effective sealing between the rotating sealing member and ashaft upon which same is mounted but will permit easy axial slidingmovement thereof in order for the seal to move axially and compensatefor wear.

4. To provide a secondary packing for a mechanical seal in which thereis no relative movement between the seal material and adjacent metallicparts whereby to minimize or eliminate fretting of such parts andconsequent failure of the seal by leakage through the irregularities inthe metal parts thereby created.

5. To provide a secondary packing for a mechanical seal having amulti-part construction wherein one of said parts will tend to shieldfrom the deposit of contaminants, or tend if such contaminants aredeposited, to wipe same off from, a zone into which another portion ofthe seal will move as the seal compensates for wear and thereby permitsuch movement to take place easily and effectively.

Other objects and purposes of the invention will be apparent to personsacquainted with apparatus of this general type upon reading thefollowing disclosure and inspection of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 of the drawing shows inone-half central section a typical seal of the type above-mentionedutilizing a secondary packing incorporating the invention.

FIG. 2 shows a modification of the secondary packing shown in FIG. 1.

FIG. 3 shows a further modification of the secondary packing shown inFIG. 1.

SUMMARY OF THE INVENTION In a conventional mechanical seal having anannular chamber for the reception of conventional secondary packing,there is provided according to the present invention a compositesecondary packing which comprises at least two axially arranged annularpacking members, one thereof being substantially rigidly associated withsaid rotating seal ring and the other thereof being substantiallyrigidly associated with the shaft. Said two packing members then bearagainst each other and the materials of said packing members are sochosen to be of sufficient flexibility and sealing capacity therebetweento permit normal motion of the rotating seal ring relative to the shaftwithout damage to such packing members or loss of sealing effecttherebetween.

Means are provided for urging said members against each other whilesimultaneously urging one of them tightly against the seal ring but onlylightly, if at all, against the shaft and urging the other thereoftightly against the shaft but only lightly, if at all, against the sealring. Said rings may be made of any convenient material such as, as inthe disclosed embodiment, laminated graphite for the packing memberbearing against the rotating sealing ring and a TF E fluorocarbon forthe packing member bearing against the shaft.

DETAILED DESCRIPTION Referring to the drawings, particularly to FIG. 1thereof, there is shown a mechanical seal which is substantiallyconventional excepting for the secondary packing and the membereffecting compression thereof. Said mechanical seal insofar as saidinvention is concerned may be of any form wherein the so-calledpush-type secondary packing is used and it may be utilized in any typeof machinery in which such packing is needed, such as pumps orautoclaves.

Referring first to the conventional portion of the seal for convenientreference purposes there is shown a cylindrical member 1 which is hereutilized to define a stuffing box 2 which, for purposes of illustration,will be assumed to project in a normal manner from the side of a rotarypump. A gland ring 3 is fixed to the outer or free end of thecylindrical housing 1 and may be fixed thereto in any convenient manner,such as by bolts or machine screws. An annular recess 4 is providedinternally of the gland ring for reception of a conventional nonrotatingsealing ring or insert 6 which may be affixed thereto in any convenientmanner, such as by being press-fitted thereinto. A further packing 7 isoften utilized between said insert and the gland ring and same may be ofany desired type, such as conventional O-ring construction or laminatedgraphite rings as set forth in the above-mentioned US. Pat. No.3,655,206. Said insert 6 has a sealing face 8 which in this embodimentis of limited radial extent to provide a chamber 9 for conventional andknown purposes.

Associated with said insert 6 there is provided a conventional rotatingsealing ring 11 having a sealing face 12 cooperating with the sealingface 8 of the insert and is provided with a conventional, internal,annular recess 10 coaxial therewith and extending thereinto from therearward end thereof for reception of the secondary packing. The sealring 11 is also provided with a plurality of circumferentially spaced,axially extending, slots 13 for the reception of driving pins 14. Saiddriving pins are fixed, as by press-fitting, into a compression ring 16and urged toward the seal ring 11 by springs 17, which springs arebacked by being received into suitable circumferentially spaced openings18 in an annularclamp collar 19. The clamp collar is fixed to the shaft21 of the machine in any convenient manner, such as by a set screw, notshown.

All of the foregoing is conventional, will be familiar to thoseacquainted with the art, and may be varied widely within the scope ofthe present invention.

Turning now to the portions of the seal assembly comprising the presentinvention, there is provided a first packing component 22 comprising atleast one packing ring snugly received into the recess 10 and made of arelatively, stiff or rigid and pressure-resistant material. In thepresent illustrative embodiment, said packing component 22 is made froma plurality of thin graphite rings of the nature shown in theabovementioned US. Pat. No. 3,655,206. Said component 22 will normallybear, at least as a matter of convenience, against the cylindricalsurface A of the recess 10 but, as hereinafter set forth further,iscaused to bear sealingly against the radial surface 108 thereof. Saidpacking component 22 also may be of such dimension that its internaldiameter is a selectably variable amount greater than that of the shaftwhereby the space 23 therebetween may be freely chosen according to avariety of circumstances to be served. The choosing of the magnitude ofthe space 23 will be dealt with further below.

A second annularpacking component 24 comprises at least one packing ringprovided axially adjacent the first packing component 22. Said component24 is provided with a rearwardly sloping surface 26 which cooperateswith a correspondingly sloping surface 27 on the forwardly projectingportions 28 of the compression member 16. The internal surface 29 ofsaid component 24 may bear against said shaft throughout its length asshown in FIG. 1 or it may be provided with grooves and lands, (as shownat 24A in FIG. 2 or 248 in FIG. 3) in order to cause said lands to bearmore tightly against the shaft than would be the case for the structureshown in FIG. 1. A projecting rib 31 is provided at the forward (hereleftward) face of the second component 24 for bearing against therearward (here rightward) face of the first component 22. For reasonswhich will be apparent hereinafter, the radial extent of the projection31 is limited to a small part of the corresponding extent of thecomponent 22 and is located roughly midway between the inner and outersurfaces thereof.

Said second component 24 is made of any material which can seal snuglyto said shaft and yet slide with respect thereto and particularly whichis sufficiently, flexible and'resilient to effect a good sealingrelationship to the material from which component 22 is made. In theparticular embodiment. herein utilized for illustrative purposes, thecomponent 24 is made of TFE fluorocarbon (Teflon).

Obviously, other materials can be utilized as needed and are availablefor both packing components, providing only that the material ofcomponent 22 can seal snugly to the seal ring 11, the material ring 24can seal snugly to the shaft, both materials will seal and flux withrespect to each other, both components have the required mechanicalstrength in view of the pressures to which the seal is being subjectedand both components have the necessary chemical characteristics toresist corrosion by the fluid being handled within the pump or othermechanism.

OPERATION In considering the operation of apparatus embodying theinvention, it should first be mentioned that the seal as a whole willoperate in the manner already well known for conventional seals of thistype. Further, the operation of the seal as a whole will be conventionalregardless of whether same is an unbalanced seal as shown in thedrawings or a balanced seal as is also well known to the art. It will besufficient, therefore, to direct express attention only to the operationof the secondary packing portion thereof.

Directing attention now to the packing itself, it will be recognizedthat the springs 17 will in a conventional manner urge the compressionring 16 leftwardly as shown in FIG. 1. Additionally, pressure in chamber2 is applied to the rearwardly sloping surface of the packing component24 and creates thereon a force having both axially leftward and radiallyinward components. The radially inward component will compress saidcomponent 24 tightly against the shaft whereby effectively to preventleakage between said component 24 and the shaft. The leftwardly axiallydirected component will urge the rib 31 strongly against the packingcomponent 22 whereby to urge same snugly against the surface 108 of therotating seal ring 11 and thereby prevent leakage both between the twopacking components 22 and 24 and between the packing components 22 andthe surface 108. Thus, an effective seal is created between the rotatingsealing ring 11 and the shaft 21. The usual seal between the surfaces 8and 12 of the two sealing rings and between the sealing ring 9 and thegland ring 3 will complete the sealing between the internal chamber 2 ofthe stuffing box housing 1 and the exterior thereof.

It is, of course, known that regardless of the care wit which therotating sealing ring and the insert are made, and regardless of thecare with which the parts are assembled, there will necessarily be acertain amount of wobble between the seal ring 11 and the shaft 21.However, with this shaft packing since the component 22 is pressedsnugly against the surface 10B, none of such wobble will result inrelative movement between said seal ring and the stiff packing component22. Thus, there can be no fretting of the seal ring by relative movementwith respect thereto of the packing component 22. Similarly, the forceof the compression ring 16 as above pointed out clamps the packingcomponent 24 tightly against the shaft 21 and hence there can be norelative movement between said last-named packing component and theshaft and therefore no fretting created on the shaft by the packingcomponent 24. The relative movement, therefore, is taken up between therib 31 and the surface of the packing component 22 immediately adjacentthereto. However, inasmuch as these surfaces are somewhat resilient andare both sealing surfaces, such relative movement will not destroy Itbeing obviously desirable to hold the seal ring 11 centered with respectto the axis of the shaft 21, same can be accomplished by so dimensioningradially either or both of the two packing rings so that either or bothof them substantially fill the space between the internal surface 10A ofthe rotating seal ring and the surface of the shaft 21 but withoutexerting any appreciable pressure on either thereof. Thus, the packingring 22 may be of such internal and external diameter that it justtouches both the surface 10A and the surface of the shaft 21 (as at 22Ain FIG. 2) without exerting appreciable pressure on either thereof andthis will adequately support and center the seal ring 11. Similarly,either additionally or alternatively, both the outer diameter and innerdiameter of the packing component 24 may be made such that when thepacking ring 24 is pressed tightly against the shaft 21, and the partsare at operating temperature, the outermost cylindrical surface 30(FIGS. 1 and 3) thereof will just touch without pressing appreciablyagainst the surface A of the seal ring 11 or may be slightly spacedtherefrom as at 30A in FIG. 2. Thus, where so touching this ring too canfunction to assist in holding the seal ring properly centered withrespect to the shaft, but without any attempt to impose a sealingrelationship between said packing component 24 and the surface 10A ofthe seal ring. A typical, but nonlimiting, dimensional differencebetween the radius of the surface 10A and the radius of the outermostcylindrical surface of the packing component 24 will be 0.005 inch.

Returning now to the clearance at 23, same may vary from zero toapproximately 0.010 inch, the larger dimension being useable where thepacking component 24, or some penetration of the rib 31 into the packingring 22, or both of them, is relied upon to center the seal ring 11 orwhere the rate of rotation of the shaft and seal ring is. sufficientlylow that a slight offcentering of the seal ring is of no consequence.However, where the space 23 is of minimal radial extent (FIG. 2), suchthat the inner surface of the packing component 22 is in light contactwith, but under no measurable pressure against, the surface 21, thenthere is obtained the additional advantage that in cases where acondensible or depositable material leaking between the seal faces 8 and12 is deposited on the shaft 21, the packing component 22, beingrelatively stiff, will act as a wiper along the shaft as same movesleftwardly in response to wear between the relatively moving parts andthereby permit an easy sliding movement leftwardly of the packingcomponent 24 along the shaft in response to pressures applied asabove-described to the compression ring 16. This minimizes or eliminatesthe hang-up which often otherwise occurs, principally with balancedseals, when the portion of the secondary packing sealing against theshaft is required to slide therealong and similtaneously push awaymaterials which have deposited on the shaft immediately in front of saidpacking. In some cases where such materials harden on the shaft andcannot be wiped or pushed away, the normal wobble of the seal ring 11will cause the lower forward (leftward) corner 25 of the component 22(or 22A) to bear against, and wear or degrade against, such hardeneddeposits. in this case, however, in contrast to where the graphitepacking is the sole packing, such degrading of the radially inner edge25 does not destroy the seal but instead often merely permits thecomponents 22, 22A, to move leftwardly and follow the wear of the sealring 11.

It has been observed that in certain cases where a packing made in themanner of the above-mentioned U.S. Pat. No. 3,655,206 and utilizinglaminated graphite only (as if the packing 22 were urged into sealingrelationship with both the surface 103 and the shaft) will causefretting of even a stainless steel shaft in two days of operation, thepacking of the present invention has been caused to operate underidentical conditions for test periods involving many days without anyvisually discernible damage to the metal surfaces at all. Since the rib31 will tend to penetrate into the packing 22, or if the rib 31 is notused, the leftward surface of the packing 24 may lie fully against therightward surface of the packing 22, there may be some tendency, wherethe space 23 is in any amount above zero, for the forward innermostcorner of the packing 22 to extrude leftwardly into the space 23. Thus,where it is desired for operational or assembly convenience that suchspace be greater than zero, its magnitude will be limited by thetendency of the packing component 24 to extrude into said space which inturn will be a function of the material from which said component 24 ismade and the pressure to which it is subjected. As above mentioned inthe case where said component 24 is made of TFE fluorocarbon, andpressures of 750 p.s.i. may be applied within the chamber 2, the space23 has been made as large as 0.010 inch without any noticeable extrusionthereinto by the ring 24. Similarly, as is frequently the case, wherethe relatively rigid component 22 is made of laminated graphite, thespace 11A between the seal ring 11 and the shaft may be as much asone-sixteenth inch.

It should be noted, however, that TFE fluorocarbon or similar materialstend to expand on heating. Accordingly, the outside diameter of thepacking component 24 must be selected with such expansion in mind sothat even when so expanded it will do more than barely touch the surface10A and will definitely not seize same or press with any great degree offorce thereagainst.

While the angle between the sloped faces 26 and 27 and the axis of theshaft is in this embodiment shown as approximately 45, same may varysomewhat in either direction, according to the material of which theshaft packing 24 is made and the pressure to which same is subjected.However, the limits for fluorocarbon types of material appear to bebetween approximately and approximately 30 inasmuch as the 30 angleseals effectively but grips the shaft so strongly that axial movementtherealong is difficult and a 60 angle in some cases does not grip theshaft with sufficient force to effect a reliable sealing.

It will also be recognized that with the invention herein shown thereare utilized two separate packing components, either of which would havesome degree of packing effectiveness if used alone. Thus, an addeddegree of safety is provided against catastrophic seal breakdowns foreven if one packing component fails, the other will at least inhibitleakage until the failure can come to the attention of maintenancepersonnel and equipment shut down for repair. This is obviously a greatadvantage in handling dangerous fluids, such as highly corrosive fluidsor radioactive fluids.

Inasmuch as a relatively rigid material can be chosen, and in theillustrated embodiment is chosen, for the packing component 22, same canprovide a high level of support for the usually softer packing component24 and thereby enable the secondary packing as a unit to withstand muchhigher pressures than present conventional secondary 'packings cannormally handle. Thus, since the remainder of the seal is adequatelystrong to handle relatively high pressures, seals equipped with asecondary packing of the invention are able to handle much higherpressures than under previous practice. The maximum pressure attainablehas not yet been ascertained but it is at least 750 p.s.i. for seals ofconventional unbalanced design as shown in the drawings and adapted tofrequently utilized shaft sizes, such as shafts of l to 4 inchesindiameter.

Contrastingly, while it is preferably for obtaining the full benefits ofthe invention as above-described to make the component 22 of a hard andstiff material and the component 24 of a softer, more conformable,material, other arrangements are possible within the scope of theinvention and one of its advantages is the opportunity so afforded tochoose materials as appropriate. For example, in a relatively lowpressure operation, both packing components can be made of afluorocarbon or of a rubber (though still perferably of differentdegrees of rigidity), which arrangement will still be an effective sealand will still minimize fretting.

While certain specific embodiments of the invention have been chosen toillustrate same, it will be recognized by those skilled in the art thatthe principles herein set forth are applicable in a widely varyingarrangement of parts and with a wide range of specific packingmaterials. Accordingly, such variations will be included within thescope of the hereinafter appended claims excepting as said claims bytheir express terms require otherwise.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

What is claimed is:

1. In a mechanical seal assembly operatively positioned between astuffing box housing and a shaft relatively rotatable with respectthereto, said assembly including a seal ring rotatable with said shaftand bearing sealingly against a nonrotating sealing ring fixed withrespect to saidstuffing box housing whereby the plane of said seal ringtends during normal operation to move angularly with respect to the axisof said shaft, the combination comprising:

a first ringlike annular packing component encircling said shaft andhaving a first face thereon bearing sealingly against said seal ring,said first packing component being free from a bearing relationship withrespect to said shaft;

a second ringlike annular packing component encircling said shaft andbeing sealingly engaged with said shaft and axially slidable withrespect thereto, said second packing component having a first surfacethereon bearing sealingly against a second face of said first packingcomponent, said second packing component also having a second surfacewhich is of a conical configuration;

mechanical means urging said second packing component sealing againstsaid shaft and against said first packing component;

said mechanical means including a compression ring surrounding saidshaft and having a conical face in engaging relationship with the secondsurface of said second packing component, whereby axially directedpressure applied to said compression ring imposes a force onto saidsecond packing component which has both a radially inwardly directed acomponent and an axially directed component.

2. A mechanical seal assembly according to claim 1, wherein said sealring has a cylindrical surface encircling both of said annular packingcomponents and wherein said second packing component is dimensioned atits outer surface so that at its operating temperature it will not exertany appreciable pressure against the surrounding cylindrical surface ofthe seal ring.

3. A seal assembly according to claim 1, wherein said first surface hasan annular rib arranged thereon for bearing against said second facewhereby to concentrate and intensify the sealing force existing betweensaid first and second packing components, said annular rib having aradial width less than the radial width of said first packing componentso that said annular rib sealingly bears against said first packingcomponent at a location spaced inwardly and outwardly from the inner andouter peripheries, respectively, of said first packing component.

4. A seal assembly according to claim 1, wherein said first packingcomponent is comprised of a lamination of graphite disks.

5. A seal assembly according to claim 1, wherein the first face of saidfirst packing component is disposed within a plane which extendssubstantially radially relative to the axis of said shaft, said firstface being disposed in sealing engagement with a bearing surface formedon said seal ring with said bearing surface also lying within a planewhich extends substantially radially relative to the axis of said shaft;

the second face of said first packing component and the first surface ofsaid second packing component each lying in planes which extendsubstantially radially relative to the axis of said shaft; and

the second surface of said second packing component being disposed onthe side of said second packing component which is opposite said firstsurface, said second surface diverging conically outwardly relative tothe axis of said shaft in a direction toward said first packingcomponent, said second packing component also having an inner annularsurface which is urged into sealing engagement with the periphery ofsaid shaft due to the radial inward compression of said second packingcomponent by said compression ring.

6. A seal assembly according to claim 1, wherein the second packingcomponent comprises a fluorocarbon material.

7. A seal assembly according to claim 1, wherein said first packingcomponent is of a relatively rigid material, and wherein said secondpacking component is of a relatively flexible material.

8. A seal assembly according to claim 1, wherein said first packingcomponent has an inner peripheral surface which is spaced from thesurface of said shaft to prevent said first packing component fromfretting or damaging the shaft.

9. A seal assembly for use with a shaft, said seal assembly including asealing ring rotatable with and loosely encircling said shaft, saidsealing ring being mounted to permit limited tilting thereof relative tosaid shaft, packing means coacting between said sealing ring and saidshaft for creating a fluid tight seal therebetween, and mechanical meansfor urging said packing means sealingly against said shaft and againstsaid sealing ring, said mechanical means including a compression ringencircling said shaft for axially compressing said packing means betweensaid sealing ring and said compression ring, and means nonrotatablycoupling said sealing ring and said compression ring while enablingrelative axial movement therebetween, comprising the improvementwherein:

said packing means includes first and second packing rings encirclingsaid shaft and positioned axially adjacent one another, said firstpacking ring being of substantially rectangular cross-section and havingone end face thereof maintained in sealing engagement with one of saidsealing and compression rings, the other end face of said first packingring being maintained in bearing and sealing engagement with an adjacentface of said second packing ring, said second packing ring also having aconical bearing surface thereon maintained in sealing and bearingengagement with an adjacent conical face formed on the other of saidsealing and compression rings.

10. A seal assembly according to claim 9, wherein both of said first andsecond packing rings are constructed of a non-metallic material, one ofsaid packing rings being relatively flexible and the other packing ringbeing relatively rigid.

11. A seal assembly according to claim 9, wherein one of said packingrings is of a laminated construction.

dial width of the adjacent face of said first packing ring. t

1. In a mechanical seal assembly operatively positioned between astuffing box housing and a shaft relatively rotatable with respectthereto, said assembly including a seal ring rotatable with said shaftand bearing sealingly against a nonrotating sealing ring fixed withrespect to said stuffing box housing whereby the plane of said seal ringtends during normal operation to move angularly with respect to the axisof said shaft, the combination comprising: a first ringlike annularpacking component encircling said shaft and having a first face thereonbearing sealingly against said seal ring, said first packing componentbeing free from a bearing relationship with respect to said shaft; asecond ringlike annular packing component encircling said shaft andbeing sealingly engaged with said shaft and axially slidable withrespect thereto, said second packing component having a first surfacethereon bearing sealingly against a second face of said first packingcomponent, said second packing component also having a second surfacewhich is of a conical configuration; mechanical means urging said secondpacking component sealing against said shaft and against said firstpacking component; said mechanical means including a compression ringsurrounding said shaft and having a conical face in engagingrelationship with the second surface of said second packing component,whereby axially directed pressure applied to said compression ringimposes a force onto said second packing component which has both aradially inwardly directed component and an axially directed component.2. A mechanical seal assembly according to claim 1, wherein said sealring has a cylindrical surface encircling both of said annular packingcomponents and wherein said second packing component is dimensioned atits outer surface so that at its operating temperature it will not exertany appreciable pressure against the surrounding cylindrical surface ofthe seal ring.
 3. A seal assembly according to claim 1, wherein saidfirst surface has an annular rib arranged thereon for bearing againstsaid second face whereby to concentrate and intensify the sealing forceexisting between said first and second packing components, said annularrib having a radial width less than the radial width of Said firstpacking component so that said annular rib sealingly bears against saidfirst packing component at a location spaced inwardly and outwardly fromthe inner and outer peripheries, respectively, of said first packingcomponent.
 4. A seal assembly according to claim 1, wherein said firstpacking component is comprised of a lamination of graphite disks.
 5. Aseal assembly according to claim 1, wherein the first face of said firstpacking component is disposed within a plane which extends substantiallyradially relative to the axis of said shaft, said first face beingdisposed in sealing engagement with a bearing surface formed on saidseal ring with said bearing surface also lying within a plane whichextends substantially radially relative to the axis of said shaft; thesecond face of said first packing component and the first surface ofsaid second packing component each lying in planes which extendsubstantially radially relative to the axis of said shaft; and thesecond surface of said second packing component being disposed on theside of said second packing component which is opposite said firstsurface, said second surface diverging conically outwardly relative tothe axis of said shaft in a direction toward said first packingcomponent, said second packing component also having an inner annularsurface which is urged into sealing engagement with the periphery ofsaid shaft due to the radial inward compression of said second packingcomponent by said compression ring.
 6. A seal assembly according toclaim 1, wherein the second packing component comprises a fluorocarbonmaterial.
 7. A seal assembly according to claim 1, wherein said firstpacking component is of a relatively rigid material, and wherein saidsecond packing component is of a relatively flexible material.
 8. A sealassembly according to claim 1, wherein said first packing component hasan inner peripheral surface which is spaced from the surface of saidshaft to prevent said first packing component from fretting or damagingthe shaft.
 9. A seal assembly for use with a shaft, said seal assemblyincluding a sealing ring rotatable with and loosely encircling saidshaft, said sealing ring being mounted to permit limited tilting thereofrelative to said shaft, packing means coacting between said sealing ringand said shaft for creating a fluid tight seal therebetween, andmechanical means for urging said packing means sealingly against saidshaft and against said sealing ring, said mechanical means including acompression ring encircling said shaft for axially compressing saidpacking means between said sealing ring and said compression ring, andmeans nonrotatably coupling said sealing ring and said compression ringwhile enabling relative axial movement therebetween, comprising theimprovement wherein: said packing means includes first and secondpacking rings encircling said shaft and positioned axially adjacent oneanother, said first packing ring being of substantially rectangularcross-section and having one end face thereof maintained in sealingengagement with one of said sealing and compression rings, the other endface of said first packing ring being maintained in bearing and sealingengagement with an adjacent face of said second packing ring, saidsecond packing ring also having a conical bearing surface thereonmaintained in sealing and bearing engagement with an adjacent conicalface formed on the other of said sealing and compression rings.
 10. Aseal assembly according to claim 9, wherein both of said first andsecond packing rings are constructed of a non-metallic material, one ofsaid packing rings being relatively flexible and the other packing ringbeing relatively rigid.
 11. A seal assembly according to claim 9,wherein one of said packing rings is of a laminated construction.
 12. Aseal assembly according to claim 11, wherein said first packing ring isconstructed of graphite and is positioned so that the inner peripheralsurface thereof does not Exert any appreciable pressure on the surfaceof said shaft.
 13. A seal assembly according to claim 12, wherein saidsecond packing ring has an annular rib arranged on the face thereofwhich is disposed in sealing engagement with the adjacent face of saidfirst packing ring, said annular rib having a radial width less than theradial width of the adjacent face of said first packing ring.